IIoT-Supported Manufacturing-Material-Flow Tracking in a DES-Based Digital-Twin Environment

Round 1

Reviewer 1 Report

-This work presents a solution that uses discrete event-driven simulations as a more efficient and accurate digital twin environment by improving the synchronization between the real and simulation layers.

-The Discrete Event Simulation-based digital layer is updated in real time to create a live digital twin; the system can identify and accurately track the product through the production cycle while updating the digital twin in real time. The algorithm running on the microcontroller can even be used independently to collect the input parameters needed for the simulation of production processes.

The implemented environment can be an adequate testbed to research the practical usability of digital twin solutions.

==>The work is rigorous and well presented, however I have a few questions:

- what is the difference between your method and the supervision of DES in general?

- There is software to remotely supervise and control production lines, which software did you use?

- I did not see a section in your article highlighting comparisons with other papers in the field in order to show the effectiveness of your methodology?

I can recommend one:

Paper: PLC-based implementation od supervisory control for flexible manufacturing systems using theory of regions, 2019.

Author Response

See the attached PDF document. In the end of it, you can find a comparison section in which all the changes are tracked.

Author Response File: Author Response.pdf

Reviewer 2 Report

Too many keywords and not all specific to the research. Reduce and re-formulate them.

The Introduction could be better if supported by more references.

The first paragraph in "Related Work" (lines 50-57) sound inappropriate for a scientific work. The overview of the literature should be short but complete. 

The overview of the Related work is not overview  of Industry 4.0. Lines 57-97 seems more appropriate for the Introduction.

What DES stands for? The abbreviation is not introduced in the text. 

Provide some proof that the sample system "meet the main requirements of I4.0". May be some references. Or explanation.

The terms OPC-UA and MQTT should be described, or referenced.

In figure 3, it is not shown what are the measurement unit on the Y axis.

Some of the figures provide no information - firgures 1 and 2. Figure 4 better suits in their place. Figure 4 itself do not need pictures and color. It can be simplified.  

Author Response

See the attached PDF document. In the end of it, you can find a comparison section in which all the changes are tracked.

Author Response File: Author Response.pdf

Reviewer 3 Report

Thanks for share your work related to digital twins in the manufacturing sector. Your contribution is both timely and interesting. I believe that it its publication will be of interest for the readers of the journal. Below you can find a few points that I would like you to consider in order to make your publication more valuable:

Introduction:

You may want to mention also the problem of interoperability and generalizability as enablers for big data oriented approaches. Otherwise your claims of “universally applicable” may come as surprise to the readers.

Please add a section that describes how what you did advance the problems that you are mentioning.

Please add a section that describes how the rest of the paper is organized.  

2. Literature review:

   I would invite you in providing a categorization of the domains that you intend to survey as well as on the problem that the authors that you are mentioning would like to address. In addition, you may want to point to other (recent) literature reviews that have been addressing Digital Tweens, IoT, I4.o and cyber-physical systems.  You may want to add a picture and/or a table that help visualize the content.

Finally you may want to add a section that discuss the limits of a “real time” approach. As based on what you are writing you are more interested in “interactivity” or “soft-real time scenarios” or “acceptable quality of service”, the following reference may help:

Lelli, F., Maron, G., & Orlando, S. (2007). Client side estimation of a remote service execution. In Proceedings of the 15th International Symposium on Modeling, Analysis, and Simulation of Computer and Telecommunication Systems (pp. 295-302). IEEE. https://doi.org/10.1109/MASCOTS.2007.14

3 Test environment:

 Start this section by explaining what is the purpose of this test environment and what is your goal. Refer to a particular part of the paper for more information.

Explain how your “test environment” is an accurate representation of a “real environment”

Add an architectural picture of the environment that you are building

Add a column in table 1 that explain if the information is always available and in the text you may want to discuss what may happen in case of faulty reading or missing information.

4 Results and discussion:

Explain how discrepancies can easily arise and how your test environment consider this aspect and how the quality and the timing of the information that you are processing may influence this aspect

Explain the details of table 2, how do you calculated the outage time? Why you are experiencing a difference? Why the difference appear to be not sensible to the outage time? Is the accuracy that you are experiencing sufficient? Why?

Minor:

I would remove sentences like “ The authors have prepared a short, concise international literature review on the re-50 search topic of digital twins based on the most prominent publications in the literature.”

Minor, the English quality of the paper may be improved.

Author Response

See the attached PDF document. In the end of it, you can find a comparison section in which all the changes are tracked.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

I accept the paper in the present form

Author Response

Please see the attached PDF document.

Author Response File: Author Response.pdf

Reviewer 3 Report

Thanks for considering my comments and suggestion. I believe that the paper will be of interest for the readers of this journal and I encourage its publication. 

Just a minor editing issue: please consider not to use section 1.1 and 1.2 in the introduction but just "1". Also, please consider moving the literature review in section "2" 

Author Response

See the attached PDF document.

Author Response File: Author Response.pdf